This invention relates to intercom systems and more particularly to an intercom system for a key telephone system.
The telephone industry presently offers a K1A2 key telephone system consisting of a basic pre-wired mounting package that is designated as a key service unit. It contains provisions to receive associated "plug-in" units in varying combinations to meet subscriber requirements.
One feature of this key system is a rotary dial intercom. The intercom unit provides a single common talking path for all stations in the system. When a call is initiated, the system provides a steady busy lamp signal at all locations and causes a single burst of ringing signal at the called station only. If the called station does not answer, the calling station must re-dial the number in order to initiate a second ring burst at the called station. This requirement of re-dialing, of course, is a disadvantage.